Habitual Diets Rich in Dark-Green Vegetables Are Associated with an Increased Response to n3 Fatty Acid Supplementation in Americans of African Ancestry
Habitual Diets Rich in Dark-Green Vegetables Are Associated with an Increased Response to n3 Fatty Acid Supplementation in Americans of African Ancestry
Year: 2014
Authors: O'Sullivan, A. Armstrong, P. Schuster, G.U. Pedersen, T.L. Allayee, H. Stephensen, C.B. Newman, J.W.
Publication Name: J. Nutr.
Publication Details: d0i:10.3945/jn.113.181875
Abstract:
Although substantial variation exists in individual responses to omega 3 (n3) fatty acid supplementation, the causes for differences in response are largely unknown. Here we investigated the associations between the efficacy of n3 fatty acid supplementation and a broad range of nutritional and clinical factors collected during a double blind, placebo controlled trial in participants of African ancestry, randomly assigned to receive either 2 g eicosapentaenoic acid (EPA) plus 1 g docosahexaenoic acid or corn/soybean oil placebo supplements for 6 wks. Food frequency questionnaires were administered, and changes in erythrocyte lipids, lipoproteins, and monocyte 5 lipoxygenase dependent metabolism were measured before and after supplementation. Mixed-mode linear regression modeling identified high and low n3 fatty acid response groups on the basis of changes in erythrocyte EPA abundance. Compliance was equivalent, whereas decreases in plasma triglycerides and VLDL particle sizes and reductions in stimulated monocyte leukotriene B4 production were larger in the high response group.
Although total diet quality scores were similar, the low response group showed lower estimated 2005 Healthy Eating Index subscores for dark green and orange vegetables and legumes and a lower intake of vegetables, particularly dark green vegetables. Because the findings reported here are associative in nature, prospective studies are needed to determine if dietary dark-green vegetables or nutrients contained in these foods can enhance the efficacy of n3 fatty acid supplements. (Authors abstract)
Accumulating evidence suggests that consuming the long-chain n3 FAs EPA and DHA can decrease cardiovascular disease (CVD) risk through a combination of mechanisms, including lowering of plasma TGs, decreasing heart rate and blood pressure, improving endothelial and autonomic function, and reducing inflammation. There is substantial heterogeneity in responses to n3 FA supplementation. A CVD risk associated 5 lipoxygenase gene (Alox5) promoter region polymorphism in the specificity protein 1 transcription factor is abundant in populations of African ancestry. In the present study, a secondary analysis to examine the variation in response to n3 FA supplementation in a cohort of black Americans randomly assigned by Alox5 genotype was conducted and the phenotypic association with reported habitual diets in high and low responders described. Participants in the current study were recruited on the basis of specific Alox5 gene promoter variants that have been suggested to influence the cardiovascular benefit of dietary n3 FAs. Whereas mean n3 FA responses were lower in the Alox5 ‘‘dd’’ (double allelic deletion) phenotype, these gene variants did not segregate the identified n3 Low from the n3 High phenotypes.
The authors have reported that individuals with low EPA concentration at baseline had greater dose dependent responses to n3 FA supplementation. This relation was also observed in the
current study; however, basal status did not account for the differential response between groups. Participants consuming n3 FAs showed positive correlations between post supplementation RBC EPA concentration and dietary intake of dark green vegetables and their associated nutrients, including vitamin K, folate, lutein/zeaxanthin, and vitamin B6. Moreover, pairing n3 FA supplementation with a dark-green vegetable intake of more than one third cup per day was associated with achieving an RBC EPA abundance of greater than 2 percent and an Omega 3 Index of about 8 percent the target for optimal health. In conclusion, the findings provide an indication that habitual consumption of dark-green vegetables may influence the efficacy of n3 FA supplementation. Because this study was a secondary analysis, the experimental design and cohort selection were not powered to address the hypotheses regarding vegetable intake and n3 FA supplementation response that emerged. In addition, limitations associated with compliance assessment and FFQ data collection are apparent. Therefore, to assess the broader implications of these findings, it will be critical to determine how robust low dark-green vegetable intake is in predicting a low n3 FA supplementation response phenotype and to further determine if a persons response phenotype can be altered by a change in dietary patterns. If supported, one could envisage a situation in which particular doses of n3 FAs could be recommended along with complementary guidelines (e.g., portions and types of vegetables to be consumed) on the basis of an individuals basal RBC EPA concentrations and an assessment of habitual dietary patterns. (Editors comments)
